Dyntopo adds vertices but does not deform mesh
It would appear that your custom brush type is set to simplify, change it to something that deforms the mesh.



From the manual page


  Simplify - This brush collapses short edges (as defined by the detail size) whether or not the Collapse Short Edges option is enabled. This brush has no effect if dynamic topology is not enabled. It can be found in the Brush ‣ Sculpt Tool menu.